I had trouble with the build up of pressure as well. Try a courser grind or do not tamp as hard. The courser grind fixed my problem with the blow out. Also leave the PF attached until you hear the release into the drip tray, it makes a distinctive noise.
The steam release after pouring espresso is the pressure release and is probably associated with the build up in pressure. I had this as well but after adjusting the grins I dont get this anymore.
The silicone strip may be part of your group head seal. I would remove it and see if it was damaged? :-/
I havent done this yet but the instructions are in the manual.